The disclosed invention is generally directed to ink supply systems for ink jet printers and plotters, and more particularly to techniques for purging air from ink supply tubes of an ink jet printer off-axis ink delivery system.
Ink jet printers and plotters are well known, and typically include one or more printhead cartridges, each having an ink emitting ink jet printhead and an ink reservoir. The printhead cartridges are supported by a movable print carriage that is reciprocatingly scanned across print media which is advanced between scans of the print carriage.
Since the capacity of a printhead cartridge ink reservoir must necessarily be limited to avoid an excessively large moving mass, and since the useful life of an ink jet printhead is typically greater than the capacity of the printhead cartridge ink reservoir, off-axis or off-line ink delivery systems have been designed wherein an off-axis ink supply is located remotely from the carriage and the printhead cartridge, and is coupled to the printhead cartridge reservoir by a flexible ink conveying tube.
A consideration with an off-line ink delivery system is whether the flexible ink conveying tube should be filled with ink or air when the off-line ink delivery system is shipped from the place of manufacture, for example as a replacement product or as part of an ink jet printer or plotter. A drawback of filling the ink delivery tube with ink is vapor transmission of ink components through the wall of the tube, which places a time limit on how long the ink delivery system can be stored. Filling the tube with air, on the other hand, allows for longer storage, but raises the problem of purging air from the tubes upon start up. If ink is pumped into the tube while the tube is connected to the printhead cartridge ink reservoir, air will be pumped into the printhead cartridge ink reservoir, which would make the printhead cartridge less reliable and require making the printhead cartridge larger. If ink is pumped into the tube while the tube is not connected to the printhead cartridge ink reservoir, there is a significant risk of ink spillage.